And this came as a surprise to me, tooamong 811 other taxa, Arsinoitherium nests with Gobiatherium mirificum (Fig. 3; Osborn and Granger 1932; Middle Eocene), which Wikipedia considers, “one of the last uintatheres”of which Uintatherium is the titular and most famous member. Wikipedia goes on to report, “Gobiatherium lacked knob-like horns, or even fang-like tusks. Instead, it had enlarged cheekbones and an almost spherical snout. Because of the noticeable lack of many diagnostic uintathere features (the horns and tusks), the genus is placed within its own subfamily.” Here’s where tradition and the LRT agree… but let’s push this a little further to see where it takes us within the friendly confines of the current LRT taxon list.

Figure 3. Gobiatherium skull (A. M. 26624) in three views. Though not immediately apparent, Gobiatherium is closest to Arsinoitherium in the LRT. Image from Osborn and Granger 1932.

Among all tested placental taxa, and despite distinct overall appearancesonly Arsinoitherium and Gobiatherium:

redevelop the ascending process of the premaxilla, completely enclosing the naris;

produce a wide, elevated set of nasals, further expanding into horns in Arsinoitherium;

only two molars, rare among placentals;

and no other condylarths have a wide flat cranium, usually a crest or a convex cranium is present.

That premaxillary ascending processlooks so normal. But among marsupial and placental mammals it is very rare indeed! Of course, the LRT does not depend on one or several traits, several dozen nest Arsinoitherium with Gobiatherium and their sisters.

Even without GobiatheriumArsinoitherium nests with Uintatherium. Coryphodon nests closer to Uintatherium. All descend from a sister to Thomashuxleya (Fig. 4), which we’ll look at soon in greater detail.

Figure 4. Thomashuxleya is basal to uintatheries and arsionoitheres. It is not a notoungulate, an invalid taxon.

We hold as an ideala gradual accumulation of derived traits in derived taxa, like Gobiatherium and Asinoitherium. In this clade, unfortunately we don’t have enough taxa to make that gradual accumulation of traits any more gradual than it currently is. This is the best we can do, at present, with available data and the present taxon list.

Uintatheres (Dinocerata) are no longer considered condylarths; they nest with xenungulates and pyrotheres within a clade of Meridungulata, the Uintatheriamorpha (Lorente, 2015; Muizon et al., 2000), and appear to have been the only group of panameriungulates to not colonized South America. Condylarths sensu stricto
comprises only of Procreodi, Pantodonta [= Tillodonta?], and Periptychoidea, and apparently left no descendants (Halliday et al., 2013 & 2015 in press).

Also, “only two molars” counts as a character? Really? Sure, dental formulas are important, but why pay attention only to tooth count? The morphology of molars (i.e. position, shape of cusps and ) is much more valuable. That’s how Ocepeiidae got kicked out of Condylartha; pantodont-like bunoselenodonty proved only superficially similar to barylambdids, with significant differences in lingual cusp orientation (Gheerbrant et al., 2014 & 2016).

Erdal, O., Antoine, P. O., & Sen, S. (2016). New material of Palaeoamasia kansui (Embrithopoda, Mammalia) from the Eocene of Turkey and a phylogenetic analysis of Embrithopoda at the species level. Palaeontology, 59(5), 631-655.

Muizon, C. D., & Cifelli, R. L. (2000). The “condylarths”(archaic Ungulata, Mammalia) from the early Palaeocene of Tiupampa (Bolivia): implications on the origin of the South American ungulates. Geodiversitas, 22(1), 47-150.

re: nasal traits… you may be correct, but at present, with the dataset I have, those are the results. More taxa will solve this problem, but as you know, we don’t have the pertinent taxa.

If you are a long time reader, then you know I have problems with suprageneric taxa (clades). So many are invalid as determined by the LRT. If you do find other sisters for currently included taxa, please suggest specimens or species to test, nothing like a larger clade. With the current list of taxa, which will ALWAYS be incomplete,. this is the way the computer lumps and separates them. And they make sense!

To your point on molar shapes… I’m coming to the conclusion that sometimes those plastic shapes may be more convergent than previously realized. I grant that too often only teeth are known. That’s why I’m using more or less complete specimens whenever possible.

There really is a revolution brewing here. I resurrected Condylarthra just as I resurrected Enaliosauria and created Triotosauria and Fenestrasauria, because those clades are important parts of the cladogram that has been developing here.

Finally, you’re not taking my word for it, and that’s a good thing. Whenever possible, don’t parrot the literature either. Test for yourself and let me know what you find.